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MATLAB code for Low Pass Filter (LPF) and High Pass Filter (HPF) based on Fast Fourier Transform (FFT) ¹.

filtered_data = FFT_filter_func( raw_data, [f_min f_max], plot_flag);

where

raw_data = [ time_vec data_vec]: time data time_vec [s] and time series of raw data data_vec [a.u.].

[f_min f_max]: bandpass [Hz].

plot_flag: When the argument is present, the FFT spectrum is plotted.

• FFT_filter_func.m: FFT fliter function.

• demo.m: demonstration for FFT_filter_func.m.

Input data example:

$f(t) = 4\cos( 2\pi t) + 2\cos( 2\pi 10t) + \sin( 2\pi 100t)$

• Power spectrum of input data

• 0-20Hz LPF: FFT_filter_func( data, [0 20], 1);

• 0-5Hz LPF: FFT_filter_func( data, [0 5], 1);

• 5- Hz HPF: FFT_filter_func( data, [5 Inf], 1);